Scalable, Ambient‐Dried and Humidity‐Tolerant Lamellar Wood Sponges for Building Thermal Management

ABSTRACT

Wood‐derived aerogels and sponges are promising for building insulation and radiative cooling due to their low thermal conductivity and high infrared emissivity. However, their fabrication relies mainly on energy‐intensive freeze‐drying with limited scalability. Moreover, their vulnerability to moisture‐induced performance degradation hinders practical application. Here, a scalable ambient‐drying strategy is proposed for fabricating decimeter‐scale lamellar wood sponges via a novel procedure involving chemical stripping, freezing, chemical crosslinking, and ambient drying. The chemical stripping and freezing processes transform the original honeycomb‐like wood into a lamellar structure, while chemical crosslinking stabilizes the cellulose network, thereby preventing structural collapse during ambient drying. The ambient‐dried wood sponge features a low density (∼36 mg cm ⁻³ ), high porosity (∼98%), and high compressive elasticity. Impressively, the lamellar wood sponge demonstrates humidity‐insensitive thermal insulation, maintaining an almost constant through‐plane thermal conductivity of ∼30 mW m ⁻¹ K ⁻¹ over a wide humidity range. A further TiO ₂ /PDMS coating endows the wood sponge with a high solar reflectance of 92.8% and a mid‐infrared emissivity of 93.5%, enabling effective daytime sub‐ambient radiative cooling with an average temperature drop of 7.1°C. The scalable, humidity‐tolerant wood sponges with low thermal conductivity and high radiative cooling capability represent a promising material for energy‐saving building applications.